UASp regulates expression of Arf1 cDNA (LD24904) with the amino acid change N52A that makes its GTPase activity weakly insensitive to activation by ASAP1, AGAP1 or Arf GAP1. The shRNA region targeted by P{UASp-Arf1.shRNA2} is mutated (with the encoded protein sequence maintained) to make it resistant to RNAi by P{UASp-Arf1.shRNA2}.